Wave generator and strain wave gearing

Abstract

A wave generator of a strain wave gearing is provided with a rigid plug, a wave bearing mounted to the ellipsoidal outer peripheral surface of the rigid plug, and four elastic claws that rotate integrally with the rigid plug. The balls of the wave bearing include balls in a loose state and balls in a tight state. The loose-state balls adjacent to the tight-state balls are applied with braking force by the elastic claws immediately before they transition into a tight state, and the orbital motion thereof is temporarily prevented or suppressed, whereby the gaps between the loose-state balls and the adjacent tight-state balls are secured. It is possible to prevent increase in rotational torque, damage to the balls or other defects due to ball-to-ball contact by the tight-state balls.

The invention claimed is: 
     
       1. A wave generator of a strain wave gearing comprising:
 a rigid plug having a non-circular outer peripheral surface or a non-circular inner peripheral surface; 
 a wave bearing capable of being flexed radially, the wave bearing being mounted to the non-circular outer peripheral surface or the non-circular inner peripheral surface and being flexed into a non-circular shape; and 
 a gap securing member that rotates integrally with the rigid plug, 
 wherein the wave bearing comprises:
 an inner race-side raceway surface and an outer race-side raceway surface that are flexed into a non-circular shape by the rigid plug; and 
 a plurality of rolling elements inserted between the inner race-side raceway surface and the outer race-side raceway surface, part of the rolling elements being in a loose state and the remaining rolling elements being in a tight state, and 
 
 wherein, 
 where one pair of adjacent rolling elements among the rolling elements, are referred to as a first rolling element and a second rolling element, the first rolling element being in the loose state and the second rolling element being in the tight state, 
 the gap securing member is a member for applying a braking force to the first rolling element against an orbital motion thereof in a direction toward the second rolling element, to secure a gap between the first rolling element and the second rolling element, and 
 wherein the gap securing member is a magnet that is disposed in a state capable of facing the first rolling element and applies a magnetic attraction force as the braking force. 
 
     
     
       2. A strain wave gearing comprising:
 a rigid gear; 
 a flexible gear capable of meshing with the rigid gear; and 
 the wave generator as set forth in  claim 1 . 
 
     
     
       3. The strain wave gearing according to  claim 2 ,
 wherein 
 the rigid gear is an internally toothed gear; 
 the flexible gear is an externally toothed gear disposed coaxially inside the rigid gear; 
 the wave generator is accommodated inside the flexible gear; 
 the rigid plug has a non-circular outer peripheral surface; and 
 the non-circular outer peripheral surface is an outer peripheral surface contoured to have an ellipsoidal shape, and 
 wherein 
 the gap securing member includes first to fourth gap securing members, the first to fourth gap securing member being attached to an outer peripheral edge part of the rigid plug; 
 the first and second gap securing members are attached at angular positions that are symmetrical with respect to a major axis of the ellipsoidal shape and are within less than 45 degrees from the major axis; and 
 the third and fourth gap securing members are attached at angular positions that are symmetrical with respect to the major axis and are within less than 45 degrees from the major axis, the angular positions of the third and fourth gap members being symmetrical with those of the first and second gap securing members with respect to the minor axis of the ellipsoidal shape. 
 
     
     
       4. A wave generator of a strain wave gearing, the wave generator comprising:
 a rigid plug having a non-circular outer peripheral surface or a non-circular inner peripheral surface; 
 a wave bearing capable of being flexed radially, the wave bearing being mounted to the non-circular outer peripheral surface or the non-circular inner peripheral surface and being flexed into a non-circular shape; and 
 a gap securing member that rotates integrally with the rigid plug, 
 wherein the wave bearing comprises:
 an inner race-side raceway surface and an outer race-side raceway surface that are flexed into a non-circular shape by the rigid plug; and 
 a plurality of rolling elements inserted between the inner race-side raceway surface and the outer race-side raceway surface, part of the rolling elements being in a loose state and the remaining rolling elements being in a tight state; and 
 
 wherein, 
 where one pair of adjacent rolling elements among the rolling elements, are referred to as a first rolling element and a second rolling element, the first rolling element being in the loose state and the second rolling element being in the tight state, 
 the gap securing member is a member for applying a braking force to the first rolling element against an orbital motion thereof in a direction toward the second rolling element, to secure a gap between the first rolling element and the second rolling element, 
 wherein 
 the rigid plug has a non-circular outer peripheral surface; and 
 the non-circular outer peripheral surface is an outer peripheral surface contoured to have an ellipsoidal shape, and 
 wherein 
 the gap securing member includes first to fourth gap securing members, the first to fourth gap securing member being attached to an outer peripheral edge part of the rigid plug; 
 the first and second gap securing members are attached at angular positions that are symmetrical with respect to a major axis of the ellipsoidal shape and are within less than 45 degrees from the major axis; and 
 the third and fourth gap securing members are attached at angular positions that are symmetrical with respect to the major axis and are within less than 45 degrees from the major axis, the angular positions of the third and fourth gap members being symmetrical with those of the first and second gap securing members with respect to the minor axis of the ellipsoidal shape. 
 
     
     
       5. A strain wave gearing comprising:
 a rigid gear; 
 a flexible gear capable of meshing with the rigid gear; and 
 the wave generator as set forth in  claim 4 . 
 
     
     
       6. A wave generator of a strain wave gearing, the wave generator comprising:
 a rigid plug having a non-circular outer peripheral surface or a non-circular inner peripheral surface; 
 a wave bearing capable of being flexed radially, the wave bearing being mounted to the non-circular outer peripheral surface or the non-circular inner peripheral surface and being flexed into a non-circular shape; and 
 a gap securing member that rotates integrally with the rigid plug, the gap securing member being attached to an outer peripheral edge portion of the rigid plug, 
 wherein the wave bearing comprises:
 an inner race-side raceway surface and an outer race-side raceway surface that are flexed into a non-circular shape by the rigid plug; and 
 a plurality of rolling elements inserted between the inner race-side raceway surface and the outer race-side raceway surface, part of the rolling elements being in a loose state and the remaining rolling elements being in a tight state, and 
 
 wherein, 
 where one pair of adjacent rolling elements among the rolling elements, are referred to as a first rolling element and a second rolling element, the first rolling element being in the loose state and the second rolling element being in the tight state, 
 the gap securing member is a member for applying a braking force to the first rolling element against an orbital motion thereof in a direction toward the second rolling element, to secure a gap between the first rolling element and the second rolling element and, 
 wherein 
 the gap securing member is an elastic member that is disposed in a state capable of coming in contact with the rolling elements from a lateral direction along a center axis line of the wave bearing and applies an elastic force as the braking force. 
 
     
     
       7. The wave generator of the strain wave gearing according to  claim 6 ,
 wherein 
 the elastic member is capable of being repeatedly and elastically deformed between a projecting position and a retreat position, the projecting position being at which the elastic member enters between the first rolling element and the second rolling element and the retreat position being at which the elastic member is pushed out laterally from the projecting position along the direction of the center axis line, and 
 the elastic member rotates integrally with the rigid plug while getting over side surface portions of the respective rolling elements subjected to repeated elastic deformations between the projecting position and the retreat position. 
 
     
     
       8. The wave generator of the strain wave gearing according to  claim 6 ,
 wherein 
 the rigid plug has a non-circular outer peripheral surface; and 
 the non-circular outer peripheral surface is an outer peripheral surface contoured to have an ellipsoidal shape, and 
 wherein 
 the gap securing member includes first to fourth gap securing members, the first to fourth gap securing member being attached to an outer peripheral edge part of the rigid plug; 
 the first and second gap securing members are attached at angular positions that are symmetrical with respect to a major axis of the ellipsoidal shape and are within less than 45 degrees from the major axis; and 
 the third and fourth gap securing members are attached at angular positions that are symmetrical with respect to the major axis and are within less than 45 degrees from the major axis, the angular positions of the third and fourth gap members being symmetrical with those of the first and second gap securing members with respect to the minor axis of the ellipsoidal shape. 
 
     
     
       9. A strain wave gearing comprising:
 a rigid gear; 
 a flexible gear capable of meshing with the rigid gear; and 
 the wave generator as set forth in  claim 6 . 
 
     
     
       10. The strain wave gearing according to  claim 9 ,
 wherein 
 the rigid gear is an internally toothed gear; 
 the flexible gear is an externally toothed gear disposed coaxially inside the rigid gear; 
 the wave generator is accommodated inside the flexible gear; 
 the rigid plug has a non-circular outer peripheral surface; and 
 the non-circular outer peripheral surface is an outer peripheral surface contoured to have an ellipsoidal shape, and 
 wherein 
 the gap securing member includes first to fourth gap securing members, the first to fourth gap securing member being attached to an outer peripheral edge part of the rigid plug; 
 the first and second gap securing members are attached at angular positions that are symmetrical with respect to a major axis of the ellipsoidal shape and are within less than 45 degrees from the major axis; and 
 the third and fourth gap securing members are attached at angular positions that are symmetrical with respect to the major axis and are within less than 45 degrees from the major axis, the angular positions of the third and fourth gap members being symmetrical with those of the first and second gap securing members with respect to the minor axis of the ellipsoidal shape.